Unit 2: Analyzing Univariate Data Text: Chapter 1 Exploring Data AP Stats Theme I: A / B Displaying quantitative variables: histograms; constructing and interpreting; histograms vs. bar graphs Skill: Histograms on the calculator

Vocabulary Modes is the amount of major peaks a distribution have. Unimodal is a distribution with one major peak. Bimodal is a distribution with two major peaks.

Histogram Like a bar chart, a histogram is made up of columns plotted on a graph. Usually, there is no space between adjacent columns. Here is how to read a histogram. The columns are positioned over a label that represents a quantitative variable.quantitative variable The column label can be a single value or a range of values. The height of the column indicates the size of the group defined by the column label.

Histogram – example Unimodal

Histogram – example Bimodal

Histogram – example bimodal symmetric distribution

Histogram – example Symmetric

Histogram – example Skewed right

Histogram – example Skewed left

Bar Charts versus Histograms Bar Charts each column represents a group defined by a categorical variable With bar charts, the X axis does not have a low end or a high end; because the labels on the X axis are categorical - not quantitative. As a result, it is less appropriate to comment on the skewness of a bar chart. Histograms each column represents a group defined by a quantitative variable it is always appropriate to talk about the skewness of a histogram; that is, the tendency of the observations to fall more on the low end or the high end of the X axisskewness

Examining a distribution

Histograms on the calculator video create-histograms-with-ti-83-graphing- calculator /view/ create-histograms-with-ti-83-graphing- calculator /view/

Histograms on the calculator written instruction Push “Stat” then “Edit” to bring up the L1 (list 1) field. The first step in creating a histogram, or any other data plot, is inputting the data. You’ll do that in L1. For this example, enter the numbers 21, 35, 36, 38, 40, 40, 41, 42, 45, 46, 46, 48, 49, 50, 46, 48, 49, 50, 55 and 56, pressing “Enter” between each entry. Click “2nd” then “Quit” to return to the home screen.home Enter “2nd” and “1” to display L1 on the screen and hit “Enter.” Choose “Stat Plot,” then choose any one of the four available graphs by clicking the number. For this example, select “1.” Scroll the cursor to “On” and click “Enter.” Scroll through the different types of graphs and select the histogram by highlighting it and clicking “Enter.” Input the list in which you stored the data for XList. In this example, that is L1. Leave Freq set at 1. Hit “Graph” to get the histogram. If you cannot see the graph, adjust the view by clicking “Zoom,” then highlight “9:ZoomStat” and hit enter. Your histogram will appear.

Assignment TPS 1.7, 1.8, 1.11, 1.12, 1.26